Support GUC parameter: cron.timezone

README.md

@@ -61,7 +61,7 @@ The schedule uses the standard cron syntax, in which * means "run every time per
 
 An easy way to create a cron schedule is: [crontab.guru](http://crontab.guru/).
 
-The code in pg_cron that handles parsing and scheduling comes directly from the cron source code by Paul Vixie, hence the same options are supported. Be aware that pg_cron always uses GMT!
+The code in pg_cron that handles parsing and scheduling comes directly from the cron source code by Paul Vixie, hence the same options are supported.
 
 ## Installing pg_cron
 
@@ -108,6 +108,14 @@ By default, the pg_cron background worker expects its metadata tables to be crea
 cron.database_name = 'postgres'
 ```
 
+Previously we could only use GMT time, but now you can adapt your time by setting cron.timezone. You can configure this by setting the `cron.timezone` configuration parameter in postgresql.conf.
+```
+# add to postgresql.conf
+
+# optionally, specify the timezone in which the pg_cron background worker should run (defaults to GMT). E.g:
+cron.timezone = 'PRC'
+```
+
 After restarting PostgreSQL, you can create the pg_cron functions and metadata tables using `CREATE EXTENSION pg_cron`.
 
 _Note: `pg_cron` may only be installed to one database in a cluster. If you need to run jobs in multiple databases, use `cron.schedule_in_database()`._

src/pg_cron.c

@@ -60,6 +60,7 @@
 #include "commands/extension.h"
 #include "commands/sequence.h"
 #include "commands/trigger.h"
+#include "commands/variable.h"
 #include "lib/stringinfo.h"
 #include "libpq-fe.h"
 #include "libpq/pqmq.h"
@@ -163,6 +164,8 @@ static int MaxRunningTasks = 0;
 static int CronLogMinMessages = WARNING;
 static bool UseBackgroundWorkers = false;
 
+char  *cron_timezone = NULL;
+
 static const struct config_enum_entry cron_message_level_options[] = {
 	{"debug5", DEBUG5, false},
 	{"debug4", DEBUG4, false},
@@ -298,6 +301,16 @@ _PG_init(void)
 		GUC_SUPERUSER_ONLY,
 		NULL, NULL, NULL);
 
+	DefineCustomStringVariable(
+		"cron.timezone",
+		gettext_noop("Specify timezone used for cron schedule."),
+		NULL,
+		&cron_timezone,
+		"GMT",
+		PGC_POSTMASTER,
+		GUC_SUPERUSER_ONLY,
+		NULL, NULL, NULL);
+
 	/* set up common data for all our workers */
 	worker.bgw_flags = BGWORKER_SHMEM_ACCESS | BGWORKER_BACKEND_DATABASE_CONNECTION;
 	worker.bgw_start_time = BgWorkerStart_RecoveryFinished;
@@ -934,7 +947,7 @@ ShouldRunTask(entry *schedule, TimestampTz currentTime, bool doWild,
 			  bool doNonWild)
 {
 	time_t currentTime_t = timestamptz_to_time_t(currentTime);
-	struct tm *tm = gmtime(&currentTime_t);
+	struct pg_tm* tm = pg_localtime(&currentTime_t, pg_tzset(cron_timezone));
 
 	int minute = tm->tm_min -FIRST_MINUTE;
 	int hour = tm->tm_hour -FIRST_HOUR;